Locoregional delivery of IL-13Rα2-targeting CAR-T cells in recurrent high-grade glioma: a phase 1 trial

Chimeric antigen receptor T cell (CAR-T) therapy is an emerging strategy to improve treatment outcomes for recurrent high-grade glioma, a cancer that responds poorly to current therapies. Here we report a completed phase I trial evaluating IL-13Rα2-targeted CAR-T cells in 65 patients with recurrent high-grade glioma, the majority being recurrent glioblastoma (rGBM). Primary objectives were safety and feasibility, maximum tolerated dose/maximum feasible dose and a recommended phase 2 dose plan. Secondary objectives included overall survival, disease response, cytokine dynamics and tumor immune contexture biomarkers. This trial evolved to evaluate three routes of locoregional T cell administration (intratumoral (ICT), intraventricular (ICV) and dual ICT/ICV) and two manufacturing platforms, culminating in arm 5, which utilized dual ICT/ICV delivery and an optimized manufacturing process. Locoregional CAR-T cell administration was feasible and well tolerated, and as there were no dose-limiting toxicities across all arms, a maximum tolerated dose was not determined. Probable treatment-related grade 3+ toxicities were one grade 3 encephalopathy and one grade 3 ataxia. A clinical maximum feasible dose of 200 × 106 CAR-T cells per infusion cycle was achieved for arm 5; however, other arms either did not test or achieve this dose due to manufacturing feasibility. A recommended phase 2 dose will be refined in future studies based on data from this trial. Stable disease or better was achieved in 50% (29/58) of patients, with two partial responses, one complete response and a second complete response after additional CAR-T cycles off protocol. For rGBM, median overall survival for all patients was 7.7 months and for arm 5 was 10.2 months. Central nervous system increases in inflammatory cytokines, including IFNγ, CXCL9 and CXCL10, were associated with CAR-T cell administration and bioactivity. Pretreatment intratumoral CD3 T cell levels were positively associated with survival. These findings demonstrate that locoregional IL-13Rα2-targeted CAR-T therapy is safe with promising clinical activity in a subset of patients. ClinicalTrials.gov Identifier: NCT02208362 .

Inclusion of 4-1BB Costimulation Enhances Selectivity and Functionality of IL13Rα2-Targeted Chimeric Antigen Receptor T Cells

Chimeric antigen receptor (CAR) T cell immunotherapy is emerging as a powerful strategy for cancer therapy; however, an important safety consideration is the potential for off-tumor recognition of normal tissue. This is particularly important as ligand-based CARs are optimized for clinical translation. Our group has developed and clinically translated an IL13(E12Y) ligand-based CAR targeting the cancer antigen IL13Rα2 for treatment of glioblastoma (GBM). There remains limited understanding of how IL13-ligand CAR design impacts the activity and selectivity for the intended tumor-associated target IL13Rα2 versus the more ubiquitous unintended target IL13Rα1. In this study, we functionally compared IL13(E12Y)-CARs incorporating different intracellular signaling domains, including first-generation CD3ζ-containing CARs (IL13ζ), second-generation 4-1BB (CD137)-containing or CD28-containing CARs (IL13-BBζ or IL13-28ζ), and third-generation CARs containing both 4-1BB and CD28 (IL13-28BBζ). In vitro coculture assays at high tumor burden establish that second-generation IL13-BBζ or IL13-28ζ outperform first-generation IL13ζ and third-generation IL13-28BBζ CAR designs, with IL13-BBζ providing superior CAR proliferation and in vivo antitumor potency in human xenograft mouse models. IL13-28ζ displayed a lower threshold for antigen recognition, resulting in higher off-target IL13Rα1 reactivity both in vitro and in vivo. Syngeneic mouse models of GBM also demonstrate safety and antitumor potency of murine IL13-BBζ CAR T cells delivered systemically after lymphodepletion. These findings support the use of IL13-BBζ CARs for greater selective recognition of IL13Rα2 over IL13Rα1, higher proliferative potential, and superior antitumor responsiveness. This study exemplifies the potential of modulating factors outside the antigen targeting domain of a CAR to improve selective tumor recognition.

Significance

This study reveals how modulating CAR design outside the antigen targeting domain improves selective tumor recognition. Specifically, this work shows improved specificity, persistence, and efficacy of 4-1BB-based IL13-ligand CARs. Human clinical trials evaluating IL13-41BB-CAR T cells are ongoing, supporting the clinical significance of these findings.

3D-organoid culture supports differentiation of human CAR+ iPSCs into highly functional CAR T cells

Unlimited generation of chimeric antigen receptor (CAR) T cells from human-induced pluripotent stem cells (iPSCs) is an attractive approach for "off-the-shelf" CAR T cell immunotherapy. Approaches to efficiently differentiate iPSCs into canonical αβ T cell lineages, while maintaining CAR expression and functionality, however, have been challenging. We report that iPSCs reprogramed from CD62L⁺ naive and memory T cells followed by CD19-CAR engineering and 3D-organoid system differentiation confers products with conventional CD8αβ-positive CAR T cell characteristics. Expanded iPSC CD19-CAR T cells showed comparable antigen-specific activation, degranulation, cytotoxicity, and cytokine secretion compared with conventional CD19-CAR T cells and maintained homogeneous expression of the TCR derived from the initial clone. iPSC CD19-CAR T cells also mediated potent antitumor activity in vivo, prolonging survival of mice with CD19⁺ human tumor xenografts. Our study establishes feasible methodologies to generate highly functional CAR T cells from iPSCs to support the development of "off-the-shelf" manufacturing strategies.

Off-the-shelf, steroid-resistant, IL13Rα2-specific CAR T cells for treatment of glioblastoma

BACKGROUND

Wide-spread application of chimeric antigen receptor (CAR) T cell therapy for cancer is limited by the current use of autologous CAR T cells necessitating the manufacture of individualized therapeutic products for each patient. To address this challenge, we have generated an off-the-shelf, allogeneic CAR T cell product for the treatment of glioblastoma (GBM), and present here the feasibility, safety, and therapeutic potential of this approach.

METHODS

We generated for clinical use a healthy-donor derived IL13Rα2-targeted CAR+ (IL13-zetakine+) cytolytic T-lymphocyte (CTL) product genetically engineered using zinc finger nucleases (ZFNs) to permanently disrupt the glucocorticoid receptor (GR) (GRm13Z40-2) and endow resistance to glucocorticoid treatment. In a phase I safety and feasibility trial we evaluated these allogeneic GRm13Z40-2 T cells in combination with intracranial administration of recombinant human IL-2 (rhIL-2; aldesleukin) in six patients with unresectable recurrent GBM that were maintained on systemic dexamethasone (4-12 mg/day).

RESULTS

The GRm13Z40-2 product displayed dexamethasone-resistant effector activity without evidence for in vitro alloreactivity. Intracranial administration of GRm13Z40-2 in four doses of 108 cells over a two-week period with aldesleukin (9 infusions ranging from 2500-5000 IU) was well tolerated, with indications of transient tumor reduction and/or tumor necrosis at the site of T cell infusion in four of the six treated research subjects. Antibody reactivity against GRm13Z40-2 cells was detected in the serum of only one of the four tested subjects.

CONCLUSIONS

This first-in-human experience establishes a foundation for future adoptive therapy studies using off-the-shelf, zinc-finger modified, and/or glucocorticoid resistant CAR T cells.

Chlorotoxin-directed CAR T cells for specific and effective targeting of glioblastoma

Although chimeric antigen receptor (CAR) T cells have demonstrated signs of antitumor activity against glioblastoma (GBM), tumor heterogeneity remains a critical challenge. To achieve broader and more effective GBM targeting, we developed a peptide-bearing CAR exploiting the GBM-binding potential of chlorotoxin (CLTX). We find that CLTX peptide binds a great proportion of tumors and constituent tumor cells. CAR T cells using CLTX as the targeting domain (CLTX-CAR T cells) mediate potent anti-GBM activity and efficiently target tumors lacking expression of other GBM-associated antigens. Treatment with CLTX-CAR T cells resulted in tumor regression in orthotopic xenograft GBM tumor models. CLTX-CAR T cells do not exhibit observable off-target effector activity against normal cells or after adoptive transfer into mice. Effective targeting by CLTX-CAR T cells requires cell surface expression of matrix metalloproteinase-2. Our results pioneer a peptide toxin in CAR design, expanding the repertoire of tumor-selective CAR T cells with the potential to reduce antigen escape.

Glioblastoma-targeted CD4+ CAR T cells mediate superior antitumor activity

Chimeric antigen receptor-modified (CAR-modified) T cells have shown promising therapeutic effects for hematological malignancies, yet limited and inconsistent efficacy against solid tumors. The refinement of CAR therapy requires an understanding of the optimal characteristics of the cellular products, including the appropriate composition of CD4+ and CD8+ subsets. Here, we investigated the differential antitumor effect of CD4+ and CD8+ CAR T cells targeting glioblastoma-associated (GBM-associated) antigen IL-13 receptor α2 (IL13Rα2). Upon stimulation with IL13Rα2+ GBM cells, the CD8+ CAR T cells exhibited robust short-term effector function but became rapidly exhausted. By comparison, the CD4+ CAR T cells persisted after tumor challenge and sustained their effector potency. Mixing with CD4+ CAR T cells failed to ameliorate the effector dysfunction of CD8+ CAR T cells, while surprisingly, CD4+ CAR T cell effector potency was impaired when coapplied with CD8+ T cells. In orthotopic GBM models, CD4+ outperformed CD8+ CAR T cells, especially for long-term antitumor response. Further, maintenance of the CD4+ subset was positively correlated with the recursive killing ability of CAR T cell products derived from GBM patients. These findings identify CD4+ CAR T cells as a highly potent and clinically important T cell subset for effective CAR therapy.

Regional Delivery of Chimeric Antigen Receptor-Engineered T Cells Effectively Targets HER2+ Breast Cancer Metastasis to the Brain

Purpose: Metastasis to the brain from breast cancer remains a significant clinical challenge, and may be targeted with CAR-based immunotherapy. CAR design optimization for solid tumors is crucial due to the absence of truly restricted antigen expression and potential safety concerns with "on-target off-tumor" activity. Here, we have optimized HER2-CAR T cells for the treatment of breast to brain metastases, and determined optimal second-generation CAR design and route of administration for xenograft mouse models of breast metastatic brain tumors, including multifocal and leptomeningeal disease.Experimental Design: HER2-CAR constructs containing either CD28 or 4-1BB intracellular costimulatory signaling domains were compared for functional activity in vitro by measuring cytokine production, T-cell proliferation, and tumor killing capacity. We also evaluated HER2-CAR T cells delivered by intravenous, local intratumoral, or regional intraventricular routes of administration using in vivo human xenograft models of breast cancer that have metastasized to the brain.Results: Here, we have shown that HER2-CARs containing the 4-1BB costimulatory domain confer improved tumor targeting with reduced T-cell exhaustion phenotype and enhanced proliferative capacity compared with HER2-CARs containing the CD28 costimulatory domain. Local intracranial delivery of HER2-CARs showed potent in vivo antitumor activity in orthotopic xenograft models. Importantly, we demonstrated robust antitumor efficacy following regional intraventricular delivery of HER2-CAR T cells for the treatment of multifocal brain metastases and leptomeningeal disease.Conclusions: Our study shows the importance of CAR design in defining an optimized CAR T cell, and highlights intraventricular delivery of HER2-CAR T cells for treating multifocal brain metastases. Clin Cancer Res; 24(1); 95-105. ©2017 AACR.

Optimization of IL13Rα2-Targeted Chimeric Antigen Receptor T Cells for Improved Anti-tumor Efficacy against Glioblastoma

T cell immunotherapy is emerging as a powerful strategy to treat cancer and may improve outcomes for patients with glioblastoma (GBM). We have developed a chimeric antigen receptor (CAR) T cell immunotherapy targeting IL-13 receptor α2 (IL13Rα2) for the treatment of GBM. Here, we describe the optimization of IL13Rα2-targeted CAR T cells, including the design of a 4-1BB (CD137) co-stimulatory CAR (IL13BBζ) and a manufacturing platform using enriched central memory T cells. Utilizing orthotopic human GBM models with patient-derived tumor sphere lines in NSG mice, we found that IL13BBζ-CAR T cells improved anti-tumor activity and T cell persistence as compared to first-generation IL13ζ-CAR CD8⁺ T cells that had shown evidence for bioactivity in patients. Investigating the impact of corticosteroids, given their frequent use in the clinical management of GBM, we demonstrate that low-dose dexamethasone does not diminish CAR T cell anti-tumor activity in vivo. Furthermore, we found that local intracranial delivery of CAR T cells elicits superior anti-tumor efficacy as compared to intravenous administration, with intraventricular infusions exhibiting possible benefit over intracranial tumor infusions in a multifocal disease model. Overall, these findings help define parameters for the clinical translation of CAR T cell therapy for the treatment of brain tumors.

Regression of Glioblastoma after Chimeric Antigen Receptor T-Cell Therapy

A patient with recurrent multifocal glioblastoma received chimeric antigen receptor (CAR)-engineered T cells targeting the tumor-associated antigen interleukin-13 receptor alpha 2 (IL13Rα2). Multiple infusions of CAR T cells were administered over 220 days through two intracranial delivery routes - infusions into the resected tumor cavity followed by infusions into the ventricular system. Intracranial infusions of IL13Rα2-targeted CAR T cells were not associated with any toxic effects of grade 3 or higher. After CAR T-cell treatment, regression of all intracranial and spinal tumors was observed, along with corresponding increases in levels of cytokines and immune cells in the cerebrospinal fluid. This clinical response continued for 7.5 months after the initiation of CAR T-cell therapy. (Funded by Gateway for Cancer Research and others; ClinicalTrials.gov number, NCT02208362 .).

A role for the thermal environment in defining co-stimulation requirements for CD4(+) T cell activation

Maintenance of normal core body temperature is vigorously defended by long conserved, neurovascular homeostatic mechanisms that assist in heat dissipation during prolonged, heat generating exercise or exposure to warm environments. Moreover, during febrile episodes, body temperature can be significantly elevated for at least several hours at a time. Thus, as blood cells circulate throughout the body, physiologically relevant variations in surrounding tissue temperature can occur; moreover, shifts in core temperature occur during daily circadian cycles. This study has addressed the fundamental question of whether the threshold of stimulation needed to activate lymphocytes is influenced by temperature increases associated with physiologically relevant increases in temperature. We report that the need for co-stimulation of CD4+ T cells via CD28 ligation for the production of IL-2 is significantly reduced when cells are exposed to fever-range temperature. Moreover, even in the presence of sufficient CD28 ligation, provision of extra heat further increases IL-2 production. Additional in vivo and in vitro data (using both thermal and chemical modulation of membrane fluidity) support the hypothesis that the mechanism by which temperature modulates co-stimulation is linked to increases in membrane fluidity and membrane macromolecular clustering in the plasma membrane. Thermally-regulated changes in plasma membrane organization in response to physiological increases in temperature may assist in the geographical control of lymphocyte activation, i.e., stimulating activation in lymph nodes rather than in cooler surface regions, and further, may temporarily and reversibly enable CD4+ T cells to become more quickly and easily activated during times of infection during fever.

Bioactivity and Safety of IL13Rα2-Redirected Chimeric Antigen Receptor CD8+ T Cells in Patients with Recurrent Glioblastoma

PURPOSE

A first-in-human pilot safety and feasibility trial evaluating chimeric antigen receptor (CAR)-engineered, autologous primary human CD8(+) cytotoxic T lymphocytes (CTL) targeting IL13Rα2 for the treatment of recurrent glioblastoma (GBM).

EXPERIMENTAL DESIGN

Three patients with recurrent GBM were treated with IL13(E13Y)-zetakine CD8(+) CTL targeting IL13Rα2. Patients received up to 12 local infusions at a maximum dose of 10(8) CAR-engineered T cells via a catheter/reservoir system.

RESULTS

We demonstrate the feasibility of manufacturing sufficient numbers of autologous CTL clones expressing an IL13(E13Y)-zetakine CAR for redirected HLA-independent IL13Rα2-specific effector function for a cohort of patients diagnosed with GBM. Intracranial delivery of the IL13-zetakine(+) CTL clones into the resection cavity of 3 patients with recurrent disease was well-tolerated, with manageable temporary brain inflammation. Following infusion of IL13-zetakine(+) CTLs, evidence for transient anti-glioma responses was observed in 2 of the patients. Analysis of tumor tissue from 1 patient before and after T-cell therapy suggested reduced overall IL13Rα2 expression within the tumor following treatment. MRI analysis of another patient indicated an increase in tumor necrotic volume at the site of IL13-zetakine(+) T-cell administration.

CONCLUSIONS

These findings provide promising first-in-human clinical experience for intracranial administration of IL13Rα2-specific CAR T cells for the treatment of GBM, establishing a foundation on which future refinements of adoptive CAR T-cell therapies can be applied.

Chimeric antigen receptors with mutated IgG4 Fc spacer avoid fc receptor binding and improve T cell persistence and antitumor efficacy

The success of adoptive therapy using chimeric antigen receptor (CAR)-expressing T cells partly depends on optimal CAR design. CARs frequently incorporate a spacer/linker region based on the constant region of either IgG1 or IgG4 to connect extracellular ligand-binding with intracellular signaling domains. Here, we evaluated the potential for the IgG4-Fc linker to result in off-target interactions with Fc gamma receptors (FcγRs). As proof-of-principle, we focused on a CD19-specific scFv-IgG4-CD28-zeta CAR and found that, in contrast to CAR-negative cells, CAR+ T cells bound soluble FcγRs in vitro and did not engraft in NSG mice. We hypothesized that mutations to avoid FcγR binding would improve CAR+ T cell engraftment and antitumor efficacy. Thus, we generated CD19-specific CARs with IgG4-Fc spacers that had either been mutated at two sites (L235E; N297Q) within the CH2 region (CD19R(EQ)) or incorporated a CH2 deletion (CD19Rch2Δ). These mutations reduced binding to soluble FcγRs without altering the ability of the CAR to mediate antigen-specific lysis. Importantly, CD19R(EQ) and CD19Rch2Δ T cells exhibited improved persistence and more potent CD19-specific antilymphoma efficacy in NSG mice. Together, these studies suggest that optimal CAR function may require the elimination of cellular FcγR interactions to improve T cell persistence and antitumor responses.

Engineering human T cells for resistance to methotrexate and mycophenolate mofetil as an in vivo cell selection strategy

Gene transfer and drug selection systems that enforce ongoing transgene expression in vitro and in vivo which are compatible with human pharmaceutical drugs are currently underdeveloped. Here, we report on the utility of incorporating human enzyme muteins that confer resistance to the lymphotoxic/immunosuppressive drugs methotrexate (MTX) and mycophenolate mofetil (MMF) in a multicistronic lentiviral vector for in vivo T lymphocyte selection. We found that co-expression of human dihydrofolate reductase (DHFR(FS); L22F, F31S) and inosine monophosphate dehydrogenase II (IMPDH2(IY); T333I, S351Y) conferred T cell resistance to the cytocidal and anti-proliferative effects of these drugs at concentrations that can be achieved clinically (up to 0.1 µM MTX and 1.0 µM MPA). Furthermore, using a immunodeficient mouse model that supports the engraftment of central memory derived human T cells, in vivo selection studies demonstrate that huEGFRt(+)DHFR(FS+)IMPDH2(IY+) T cells could be enriched following adoptive transfer either by systemic administration of MTX alone (4.4 -fold), MMF alone (2.9-fold), or combined MTX and MMF (4.9-fold). These findings demonstrate the utility of both DHFR(FS)/MTX and IMPDH2(IY)/MMF for in vivo selection of lentivirally transduced human T cells. Vectors incorporating these muteins in combination with other therapeutic transgenes may facilitate the selective engraftment of therapeutically active cells in recipients.

Efficient selection of genetically modified human T cells using methotrexate-resistant human dihydrofolate reductase

Genetic modification of human T cells to express transgene-encoded polypeptides, such as tumor targeting chimeric antigen receptors, is an emerging therapeutic modality showing promise in clinical trials. The development of simple and efficient techniques for purifying transgene⁺ T cells is needed to facilitate the derivation of cell products with uniform potency and purity. Unlike selection platforms that utilize physical methods (immunomagnetic or sorting) that are technically cumbersome and limited by the expense and availability of clinical-grade components, we focused on designing a selection system based on the pharmaceutical drug methotrexate (MTX), a potent allosteric inhibitor of human dihydrofolate reductase (DHFR). Here, we describe the development of SIN lentiviral vectors that direct the coordinated expression of a CD19-specific CAR, the human EGFRt tracking/suicide construct, and a methotrexate-resistant human DHFR mutein (huDHFR^FS; L22F, F31S). Our results demonstrate that huDHFR^FS co-expression renders lentivirally transduced primary human CD45RO⁺CD62L⁺ central memory T cells resistant to lymphotoxic concentrations of MTX up to 0.1 µM. Our modular cDNA design insures that selected MTX-resistant T cells co-express functionally relevant levels of the CD19-specific CAR and EGFRt. This selection system based on huDHFR^FS and MTX has considerable potential utility in the manufacturing of clinical-grade T cell products.

Antitransgene rejection responses contribute to attenuated persistence of adoptively transferred CD20/CD19-specific chimeric antigen receptor redirected T cells in humans

Immunotherapeutic ablation of lymphoma is a conceptually attractive treatment strategy that is the subject of intense translational research. Cytotoxic T lymphocytes (CTLs) that are genetically modified to express CD19- or CD20-specific, single-chain antibody-derived chimeric antigen receptors (CARs) display HLA-independent antigen-specific recognition/killing of lymphoma targets. Here, we describe our initial experience in applying CAR-redirected autologous CTL adoptive therapy to patients with recurrent lymphoma. Using plasmid vector electrotransfer/drug selection systems, cloned and polyclonal CAR(+) CTLs were generated from autologous peripheral blood mononuclear cells and expanded in vitro to cell numbers sufficient for clinical use. In 2 FDA-authorized trials, patients with recurrent diffuse large cell lymphoma were treated with cloned CD8(+) CTLs expressing a CD20-specific CAR (along with NeoR) after autologous hematopoietic stem cell transplantation, and patients with refractory follicular lymphoma were treated with polyclonal T cell preparations expressing a CD19-specific CAR (along with HyTK, a fusion of hygromycin resistance and HSV-1 thymidine kinase suicide genes) and low-dose s.c. recombinant human interleukin-2. A total of 15 infusions were administered (5 at 10(8)cells/m(2), 7 at 10(9)cells/m(2), and 3 at 2 x 10(9)cells/m(2)) to 4 patients. Overt toxicities attributable to CTL administration were not observed; however, detection of transferred CTLs in the circulation, as measured by quantitative polymerase chain reaction, was short (24 hours to 7 days), and cellular antitransgene immune rejection responses were noted in 2 patients. These studies reveal the primary barrier to therapeutic efficacy is limited persistence, and provide the rationale to prospectively define T cell populations intrinsically programmed for survival after adoptive transfer and to modulate the immune status of recipients to prevent/delay antitransgene rejection responses.

Winner of the 2007 Society for Thermal Medicine Young Investigator Award. Fever-range whole body hyperthermia prevents the onset of type 1 diabetes in non-obese diabetic mice

PURPOSE

Type 1 diabetes (T1D) is an autoimmune disease in which the insulin producing beta cells of the pancreatic islets are destroyed by cytotoxic T lymphocytes (CTLs). It has been demonstrated that the injection of complete Freund's adjuvant (CFA) can prevent disease onset in non-obese diabetic (NOD) mice. This effect has been attributed to CFA-enhanced natural killer (NK) cell mediated control of autoimmune CTLs. Fever-range whole body hyperthermia (FR-WBH) has also been shown to stimulate NK cell cytotoxicity. This led to the hypothesis that FR-WBH can prevent disease onset in NOD mice by a thermally regulated mechanism.

METHODS

FR-WBH or mock treatment was administered weekly until the NOD mice reached 32 weeks of age. Blood glucose levels were monitored weekly, with measurements > or =33.5 mM indicating onset of diabetes, at which time the mice were euthanized for histological and cellular analyses.

RESULTS

Weekly FR-WBH prevented the onset of T1D in NOD mice and this effect correlated with increased NK cell cytotoxicity and control of blood glucose concentration. Histological analysis revealed significantly fewer lymphocytes infiltrating the pancreatic islets of FR-WBH treated mice than those of untreated mice, suggesting a relationship between thermally induced protection of beta cells and their ability to regulate blood glucose concentrations.

CONCLUSIONS

These studies show, for the first time, that mild systemic hyperthermia can prevent the generation of T1D in a clinically relevant mouse model. Further study of the thermally sensitive aspects of immunoregulation could lead to the development of heat-based therapies for the prevention or treatment of autoimmune diseases.

Transgene-enforced co-stimulation of CD4+ T cells leads to enhanced and sustained anti-tumor effector functioning

Background The role of co-stimulation in CD4+ T cell activation by professional APC is well established, while less is known of the role co-stimulation plays when CD4+ T cells interact directly with tumor cells. Methods Through genetic engineering of human CD4+ T cells, we tested the hypothesis that integration of co-stimulatory signaling domains within a tumor-targeting chimeric Ag receptor (CAR), the IL-13Ralpha2-specific IL-13-zetakine (IL13zeta), would enhance CD4+ T cell mediated responses against tumors that fail to express ligands for co-stimulatory receptors. Results Compared with CD3zeta-mediated activation alone, CD4+ effector T cells expressing the IL13-CD28-41BBzeta CAR exhibited augmented/sustained MAPK and AKT activity, up-regulated Th1 cytokine production, and enhanced cytolytic potency against tumor targets. Moreover, upon recursive stimulation with tumor, the IL13-CD28-41BBzeta+ cells retained/recycled their lytic function, whereas IL-13zeta+ CD4+ cells became anergic/exhausted. These in vitro observations correlated with enhanced in vivo control of established orthotopic CNS glioma xenografts in immunodeficient mice mediated by adoptively transferred ex vivo-expanded CD4+ T cells expressing the co-stimulatory CAR. Discussion Together these studies demonstrate the importance of integrating co-stimulation with CD3zeta signaling events to activate fully CD4+ anti-tumor effector cells for sustained function in the tumor microenvironment.

Enhancement of natural killer (NK) cell cytotoxicity by fever-range thermal stress is dependent on NKG2D function and is associated with plasma membrane NKG2D clustering and increased expression of MICA on target cells

Circulating NK cells normally experience temperature gradients as they move about the body, but the onset of inflammation can expose them and their targets to febrile temperatures for several hours. We found that exposure of human peripheral blood NK cells and target cells to fever-range temperatures significantly enhances lysis of Colo205 target cells. A similar effect was not observed when NK cell lines or IL-2-activated peripheral blood NK cells were used as effectors, indicating that thermal sensitivity of effectors is maturation or activation state-dependent. Use of blocking antibodies revealed that this effect is also dependent on the function of the activating receptor NKG2D and its ligand MHC class I-related chain A (MICA). On NK cells, it was observed that thermal exposure does not affect the total level of NKG2D surface expression, but does result in its distinct clustering, identical to that which occurs following IL-2-induced activation. On tumor target cells, a similar, mild temperature elevation results in transcriptional up-regulation of MICA in a manner that correlates with increased sensitivity to cytolysis. Overall, these data reveal that NK cells possess thermally responsive regulatory elements, which facilitate their ability to capitalize on reciprocal, stress-induced changes simultaneously occurring on target cells during inflammation and fever.

An important role for granulocytes in the thermal regulation of colon tumor growth

Several lines of research show that cells of the immune response are sensitive to thermal variations in their microenvironment, such as that which occurs during inflammation and fever; these data have led to the hypothesis that strategic applications of heat could assist in controlling tumor growth in animal models. The innate immune response is known to play a critical role in the development of effective anti-tumor immunity and granulocytes such as polymorphonuclear neutrophils (PMNs), as key mediators of inflammation, have been suggested to have the potential to initiate immune response cascades against tumors. Thus, we hypothesized that PMNs may play a crucial role in mediating the anti-tumor effects of a mild, fever-range whole-body hyperthermia (FR-WBH) protocol, where core body temperatures are raised to 39.5-40 degrees C for 8 hrs. Indeed, in BALB/c mice bearing the colon tumor CT26, the anti-tumor effect of WBH correlates with increased granulocytic infiltrate at the tumor site as determined using immunohistochemical analysis for Gr-1+ cells. In both BALB/c mice bearing CT26 and SCID mice bearing human colon tumors, PMN depletion in vivo using anti-Gr-1 ascites ablated the anti-tumor effect of mild WBH. Because mild thermal stress is also found to enhance the respiratory burst of granulocytes, these data collectively suggest that the thermal stimulation of granulocytes may help to prevent tumor establishment. Overall, these results may have implications for the design of thermal therapy protocols in cancer immunotherapy.

NK Cell Mediated Tumor Cytotoxicity is enhanced by Mild Thermal Stress through Heat Shock Factor 1 (50.24)

Natural killer (NK) cells directly kill tumor cells and regulate downstream adaptive immune responses. Previous studies in our lab suggest that mild thermal stress (39.5 C) significantly enhances the cytotoxicity of human peripheral blood NK cells compared to normothermic conditions (37 C) against human colon tumor cells. This enhancement was not seen when syngeneic human PBMC were used as targets, nor when the IL-2 dependent human NK cell lines NKL or NK92MI, or IL-2 activated primary NK cells were used as effectors. Thus, we hypothesized that resting NK cell cytotoxic activity is regulated by mild thermal stress. Blocking of the activating receptor NKG2D and its stress-induced ligand MICA with blocking antibodies suggested the involvement of these molecules in the thermal regulation of NK cytotoxicity. We found that inhibitory receptor KIR2DL1 levels on NK cells were not changed with thermal stress. Increased clustering of NKG2D on NK cells was observed with thermal stress, suggesting the potential for enhanced efficiency of activating signals. However prevention of lipid raft clustering with methyl B-cyclodextrin on NK cells shows no significant affect on thermally enhanced cytotoxicity. On target cells, MICA expression appeared to be upregulated by mild thermal stress in a manner that is dependent on the transcription factor HSF-1. Overall, these data suggest that thermal therapy might be clinically utilized to help enhance NK mediated tumor cell killing.

Supported by NIH P01 CA94045, R01 CA71599, Komen Foundation DISS0402487 and Fulbright Program.

Adoptive transfer of chimeric antigen receptor re-directed cytolytic T lymphocyte clones in patients with neuroblastoma

Metastatic neuroblastoma is a poor-prognosis malignancy arising during childhood that overexpresses the L1-cell adhesion molecule (CD171). We have previously described a tumor L1-cell adhesion molecule-specific, single chain antibody-derived, chimeric antigen receptor designated CE7R for re-directing the antigen-specific effector functioning of cytolytic T lymphocytes. Here, we report on the feasibility of isolating, and the safety of infusing, autologous CD8(+) cytolytic T lymphocyte clones co-expressing CE7R and the selection-suicide expression enzyme HyTK in children with recurrent/refractory neuroblastoma. The cytolytic T lymphocyte products were derived from peripheral blood mononuclear cells that were subjected to polyclonal activation, plasmid vector electrotransfer, limiting dilution hygromycin selection, and expansion to numbers sufficient for adoptive transfer. In total, 12 infusions (nine at 10(8) cells/m(2), three at 10(9) cells/m(2)) were administered to six patients. No overt toxicities to tissues known to express L1-cell adhesion molecule (e.g., central nervous system, adrenal medulla, and sympathetic ganglia) were observed. The persistence of cytolytic T lymphocyte clones in the circulation, measured by vector-specific quantitative polymerase chain reaction, was short (1-7 days) in patients with bulky disease, but significantly longer (42 days) in a patient with a limited disease burden. This first-in-humans pilot study sets the stage for clinical trials employing adoptive transfer in the context of minimal residual disease.

Altered granulopoietic profile and exaggerated acute neutrophilic inflammation in mice with targeted deficiency in the sialyltransferase ST6Gal I

Elevation of serum sialic acid and the ST6Gal-1 sialyltransferase is part of the hepatic system inflammatory response, but the contribution of ST6Gal-1 has remained unclear. Hepatic ST6Gal-1 elevation is mediated by P1, 1 of 6 promoters regulating the ST6Gal1 gene. We report that the P1-ablated mouse, Siat1DeltaP1, and a globally ST6Gal-1-deficient mouse had significantly increased peritoneal leukocytosis after intraperitoneal challenge with thioglycollate. Exaggerated peritonitis was accompanied by only a modest increase in neutrophil viability, and transferred bone marrow-derived neutrophils from Siat1DeltaP1 mice migrated to the peritonea of recipients with normal efficiency after thioglycollate challenge. Siat1DeltaP1 mice exhibited 3-fold greater neutrophilia by thioglycollate, greater pools of epinephrine-releasable marginated neutrophils, greater sensitivity to G-CSF, elevated bone marrow CFU-G and proliferative-stage myeloid cells, and a more robust recovery from cyclophosphamide-induced myelosuppression. Bone marrow leukocytes from Siat1DeltaP1 are indistinguishable from those of wild-type mice in alpha2,6-sialylation, as revealed by the Sambucus nigra lectin, and in the expression of total ST6Gal-1 mRNA. Together, our study demonstrated a role for ST6Gal-1, possibly from extramedullary sources (eg, produced in liver) in regulating inflammation, circulating neutrophil homeostasis, and replenishing granulocyte numbers.

Emerging evidence indicates that physiologically relevant thermal stress regulates dendritic cell function

Elevations in temperature that are associated with inflammation or fever have been linked to improved survival from infections, enhanced immunological functions, and increased control of tumor growth. Over the past few years, several groups have begun to explore the possible linkage among these observations and have tested the hypothesis that various immune cells are especially sensitive to thermal stimulation. However, relatively little is known regarding the effects of thermal stimulation on antigen presenting cells (APCs), such as dendritic cells (DCs). Very recently, several groups have begun to examine the ability of thermal stimuli to regulate the function of these cells which are known to play a pivotal role in the efficacy of vaccines and other immunotherapies. In this review, we summarize what has been discovered about the role of mild thermal stress in regulating various Dendritic cell (DC) activities. Excitingly, it appears that mild elevations of temperature have the potential to enhance antigen uptake, activation associated migration, maturation, cytokine expression and T cell stimulatory activity of DCs. While these studies reveal that the timing, temperature and duration of heating is important, they also set the stage for essential questions that now need to be investigated regarding the molecular mechanisms by which elevated temperatures regulate DC function. With this information, we may soon be able to maximize the strategic use of thermal therapy as an adjuvant, i.e., combining its use with cancer immunotherapies such as vaccines, which depend upon the function of DCs. Several possible strategies and timepoints involving the clinical application of hyperthermia in combination with immunotherapy are presented.

Protocols for simulating the thermal component of fever: preclinical and clinical experience

An increase in body temperature in association with inflammation or infection has been evolutionarily conserved in all cold and warm-blooded vertebrates and even in several invertebrates thus far examined. This change in temperature is strongly correlated with survival from infection in many animal models. Although the means by which body temperature is increased and maintained differs between cold- versus warm-blooded species, there are strong similarities in terms of the magnitude of temperature change and its duration. Despite these intriguing observations and significant biological sequelae, temperature manipulation is rarely considered in the context of most experimental immunological investigations. We have hypothesized that the thermal microenvironment plays a critical role in regulating events in the immune response and that an increase in ambient temperature can serve as a natural trigger or "danger signal" to the immune system. To examine the direct effects of fever-like temperatures on immunological parameters, we have designed and characterized protocols for performing whole body heating of mice and humans in vivo, and heating of cultured cells in vitro. Our studies have now progressed to the development of therapeutic uses of fever-range hyperthermia in combination with other therapies. This chapter describes the experimental procedures that have been developed for these studies and summarizes several of the immunologically relevant effects that we have noticed following mild heat treatments in vivo and in vitro.

Thermal regulation of dendritic cell activation and migration from skin explants

Dendritic cells (DCs) in the skin rapidly take up antigen and migrate out of the skin to draining lymph nodes for antigen presentation. As a result, these cells play an important role in generating specific immune responses against infectious agents that enter the skin and against antigens delivered as vaccines. Previous efforts revealed that fever-like elevations in body temperature enhance antigen-dependent immune responses initiated at the site of the skin and stimulate the migration of epidermal DCs to draining lymph nodes. Collectively, these data have led to the hypothesis that the activation of epidermal DCs is sensitive to physiological thermal stimuli. In this study, ear skin explants derived from BALB/c mice were either maintained at 37 degrees C or incubated at 40 degrees C for the first 6.5 h before being placed at 37 degrees C. This heating protocol altered the density and morphology of the epidermal DCs in a manner suggestive of an increased kinetics of activation-associated DC migration. Flow cytometric analysis of the emigrated cells also indicated that mild heating enhanced the migration kinetics of DCs and increased the DC expression of MHC class II and the activation marker CD86. Importantly, these migrated cells displayed higher stimulatory capacity in a mixed lymphocyte reaction compared to those of controls. Overall, these results suggest that mild thermal stimuli can enhance DC activation and function and that strategic applications of heat could enhance the potency of vaccines consisting of relatively weak antigens, such as cancer vaccines.

Induction of stress proteins in a panel of mouse tissues by fever-range whole body hyperthermia

When exposed to environmental stress, cell survival is supported by the upregulation of stress proteins such as heat shock proteins (HSPs) or glucose regulated proteins (GRPs), which help prevent protein denaturation. To begin to characterize the ability of a physiologically relevant heat exposure to induce stress protein expression, the cerebellum, cerebrum, colon, heart, kidney, liver, lung, lymph nodes, muscle, serum and thymus were extracted from BALB/c mice at various times after fever-range whole body hyperthermia (FR-WBH, 39.5-40 degrees C for 6 h) treatment. The expression of three stress proteins, HSP70, HSP110 and GRP170, was determined in these tissues and serum and compared to constitutive levels in control tissues and serum using Western analysis. Constitutive expression of GRP170 was not affected by FR-WBH in any tissue. In contrast, FR-WBH did enhance HSP expression: HSP70 in heart, kidney, lung, lymph nodes and thymus; and HSP110 in lung, lymph nodes and thymus. The lymphoid tissues displayed the most consistent upregulation of both HSP70 and HSP110 upon FR-WBH treatment. The apparent sensitivity of immunologically relevant tissues to FR-WBH may relate to the enhanced immune responses that are observed during febrile temperatures.

A phase I study of fever-range whole body hyperthermia (FR-WBH) in patients with advanced solid tumours: correlation with mouse models

Various studies in animal tumour models have revealed the potential of fever-range whole body hyperthermia (FR-WBH) to be used in cancer therapy. To determine the safety of FR-WBH treatment in the clinic, patients with advanced solid tumours were heated in the outpatient setting to 39-39.5 degrees C for 3 or 6h, or 39.5-40 degrees C for 6h using the Heckel-HT 2000 apparatus. These WBH treatments were well tolerated, with no significant adverse events related to cardiac, hepatic, renal or pulmonary systems. In the majority of patients, flow cytometric analysis of peripheral blood leukocyte populations indicated that there were transient decreases in the number of circulating T lymphocytes and a concomitant decrease in the number of L-selectin positive lymphocytes in the peripheral blood. These findings closely mimic the affects seen previously in pre-clinical murine studies in which this same fever-like treatment was shown to inhibit tumour growth. These studies have established the safety of this treatment and will allow for future clinical trials where application of FR-WBH treatment can be combined with other anti-cancer therapies, including immunotherapy and chemotherapy.

Regulatory potential of fever-range whole body hyperthermia on Langerhans cells and lymphocytes in an antigen-dependent cellular immune response

The febrile response is one of the most common features of infection and inflammation. However, temperature is rarely a variable in experimental immunological investigations. To determine whether the thermal microenvironment has any immunoregulatory potential in an Ag-dependent response, we applied a mild fever-range whole body hyperthermia (FR-WBH) protocol to BALB/c mice experiencing the contact hypersensitivity (CHS) reaction. We observed that the timing of this FR-WBH treatment relative to the different phases of the CHS response was crucial to the outcome. FR-WBH treatment before sensitization with a 0.5% FITC solution resulted in a depressed CHS response. This appears to be due to direct effects of FR-WBH on epidermal Langerhans cell trafficking to the draining lymph nodes. In contrast, application of FR-WBH directly after application of the elicitation dose of FITC solution resulted in an enhanced reaction. This result correlates with increased homing of lymphocytes to the site of elicitation. Overall, these data have important implications regarding the role of thermal changes experienced during infection and the clinical use of FR-WBH relative to immunotherapeutic strategies.

Fever-range hyperthermia dynamically regulates lymphocyte delivery to high endothelial venules

Fever is associated with increased survival during acute infection, although its mechanism of action is largely unknown. This study found evidence of an unexpectedly integrated mechanism by which fever-range temperatures stimulate lymphocyte homing to secondary lymphoid tissues by increasing L-selectin and alpha4beta7 integrin-dependent adhesive interactions between circulating lymphocytes and specialized high endothelial venules (HEV). Exposure of splenic lymphocytes in vivo to fever-like whole-body hyperthermia (WBH; 39.8 +/- 0.2 degrees C for 6 hours) stimulated both L-selectin and alpha4beta7 integrin-dependent adhesion of lymphocytes to HEV under shear conditions in lymph nodes and Peyer patches. The adhesiveness of HEV ligands for L-selectin and alpha4beta7 integrin (ie, peripheral lymph node addressin and mucosal addressin cell adhesion molecule-1) also increased during WBH or febrile responses associated with lipopolysaccharide-induced or turpentine-induced inflammation. Similar increases in HEV adhesion occurred during hyperthermia treatment of lymph node and Peyer patch organ cultures in vitro, indicating that the local lymphoid tissue microenvironment is sufficient for the hyperthermia response. In contrast, WBH did not augment adhesion in squamous endothelium of nonlymphoid tissues. Analysis of homing of alpha4beta7(hi) L-selectin(lo) murine TK1 cells and L-selectin(hi) alpha4beta7 integrin-negative 300.19/L-selectin transfectant cells showed that fever-range temperatures caused a 3- to 4-fold increase in L-selectin and alpha4beta7 integrin-dependent trafficking to secondary lymphoid tissues. Thus, enhanced lymphocyte delivery to HEV by febrile temperatures through bimodal regulation of lymphocyte and endothelial adhesion provides a novel mechanism to promote immune surveillance.

Regulation of immune activity by mild (fever-range) whole body hyperthermia: effects on epidermal Langerhans cells

Inflammation of the skin and systemic fever, both of which occur with injury or infection, include a hyperthermic component that many believe constitutes a physiological stress. Such increases in local or systemic body temperature may also have a regulatory effect on immune function. Langerhans cells (LCs), the dendritic cells of the skin, continuously monitor the extracellular matrix of the skin by taking up particles and microbes that they then carry to draining lymph nodes for presentation to T lymphocytes. We hypothesize that the thermal element of inflammation and/or fever may help regulate the activation and migration of LCs out of the epidermis. To test this hypothesis, Balb/ c mice were exposed to a mild (39.8 degrees C +/- 0.2 degrees C), long-duration (6 hours) whole body hyperthermia (WBH) treatment, which mimics the thermal component of fever. The number of LCs and their morphology were analyzed at various time points up to 7 days after the initiation of WBH. The LCs of the ear epidermis were visualized using a fluorescein isothiocyanate-conjugated antibody specific for the major histocompatibility complex (MHC) class II molecule and confocal microscopy. Although MHC class II staining was diffuse on the surface of the LC body and dendritic extensions of both WBH and control samples, the WBH-treated LCs exhibited a more punctate morphology with fewer dendritic processes compared with control LCs. A significant decrease in the number of LCs was also observed 1 to 5 days after WBH treatment. Furthermore, in vitro heating of Balb/c ear skin cultures at 40 degrees C for 6 to 8 hours enhanced the numbers of viable LCs that migrated into the culture wells. These results suggest that WBH treatment stimulates epidermal LCs in the absence of foreign antigen.

Regulatory effects of fever-range whole-body hyperthermia on the LPS-induced acute inflammatory response

The thermal component of fever is one of the most poorly understood aspects of inflammation. To evaluate the role of fever-range hyperthermia on acute inflammation, BALB/c and C57BL/6 mice were exposed to mild, long-duration whole-body hyperthermia (WBH), and serum concentrations of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), IL-1beta, and the acute phase proteins (APPs) alpha1-acid glycoprotein and haptoglobin were analyzed. WBH alone did not affect serum concentrations of these cytokines or APPs when compared with controls. In contrast, when WBH was applied just after intraperitoneal administration of lipopolysaccharide (LPS), serum concentrations of TNF-alpha and IL-6 were greater than or equal to threefold higher in BALB/c mice compared with LPS-treated controls. LPS-induced IL-6 levels were also enhanced in WBH-treated C57BL/6 mice. However, APP levels were prolonged only in WBH-treated BALB/c mice. It is interesting that in vitro hyperthermia treatment of LPS-stimulated peritoneal cells resulted in decreased cytokine production compared with controls. These results suggest that fever-range hyperthermia regulates acute inflammation in a mouse strain-specific manner that is more complex than that observed in vitro.

Comparison of the effects of two different whole body hyperthermia protocols on the distribution of murine leukocyte populations

Two predominant WBH protocols presently being used in clinical trials include a low temperature, long duration (LL) WBH, where core body temperature is raised to 39.5-40 degrees C for 6h or more, and a high temperature, short duration (HS) WBH, where core body temperature is raised to 41.8 degrees C for up to 2h. Here, the effects of LL-WBH and HS-WBH on leukocyte populations in the blood, spleen, lymph node (LN) and peritoneal cavity (PerC) of Balb/c mice were compared using flow cytometry. The total numbers of peripheral blood leukocytes decreased up to 2-fold immediately after LL-WBH, reflecting a decrease of lymphocyte numbers compared to controls. In contrast, the numbers of blood leukocytes are increased 2.7-fold immediately after HS-WBH compared to controls, reflecting an increase in lymphocytes, monocytes and granulocytes. After both LL- and HS-WBH treatment, leukocyte numbers in the spleen are decreased approximately 2-fold, again reflecting decreases in lymphocyte numbers. In the PerC, total numbers of leukocytes are also significantly decreased (2-fold) during LL-WBH but not HS-WBH. Total numbers of leukocytes in the LNs were unaffected by both LL- and HS-WBH. Overall, these data reveal differential effects of the LL- and HS-WBH protocols on leukocyte populations in the blood, spleen, LN and PerC of Balb/c mice.

Effect of fever-like whole-body hyperthermia on lymphocyte spectrin distribution, protein kinase C activity, and uropod formation

Regional inflammation and systemic fever are hallmarks of host immune responses to pathogenic stimuli. Although the thermal element of fever is thought to enhance the activity of immune effector cells, it is unclear what the precise role of increased body temperatures is on the activation state and effector functions of lymphocytes. We report here that mild, fever-like whole body hyperthermia (WBH) treatment of mice results in a distinct increase in the numbers of tissue lymphocytes with polarized spectrin cytoskeletons and uropods, as visualized in situ. WBH also induces a coincident reorganization of protein kinase C (PKC) isozymes and increased PKC activity within T cells. These hyperthermia-induced cellular alterations are nearly identical with the previously described effects of Ag- and mitogen-induced activation on lymphocyte spectrin and PKC. Immunoprecipitation studies combined with dual staining and protein overlay assays confirmed the association of PKC beta and PKC theta with spectrin following its reorganization. The receptor for activated C kinase-1 was also found to associate with the spectrin-based cytoskeleton. Furthermore, all these molecules (spectrin, PKC beta, PKC theta, and receptor for activated C kinase-1) cotranslocate to the uropod. Enhanced intracellular spectrin phosphorylation upon WBH treatment of lymphocytes was also found and could be blocked by the PKC inhibitor bisindolylmaleimide I (GF109203X). These data suggest that the thermal element of fever, as mimicked by these studies, can modulate critical steps in the signal transduction pathways necessary for effective lymphocyte activation and function. Further work is needed to determine the cellular target(s) that transduces the signaling pathway(s) induced by hyperthermia.

Effect of Fever-Like Whole-Body Hyperthermia on Lymphocyte Spectrin Distribution, Protein Kinase C Activity, and Uropod Formation

Regional inflammation and systemic fever are hallmarks of host immune responses to pathogenic stimuli. Although the thermal element of fever is thought to enhance the activity of immune effector cells, it is unclear what the precise role of increased body temperatures is on the activation state and effector functions of lymphocytes. We report here that mild, fever-like whole body hyperthermia (WBH) treatment of mice results in a distinct increase in the numbers of tissue lymphocytes with polarized spectrin cytoskeletons and uropods, as visualized in situ. WBH also induces a coincident reorganization of protein kinase C (PKC) isozymes and increased PKC activity within T cells. These hyperthermia-induced cellular alterations are nearly identical with the previously described effects of Ag- and mitogen-induced activation on lymphocyte spectrin and PKC. Immunoprecipitation studies combined with dual staining and protein overlay assays confirmed the association of PKCβ and PKCθ with spectrin following its reorganization. The receptor for activated C kinase-1 was also found to associate with the spectrin-based cytoskeleton. Furthermore, all these molecules (spectrin, PKCβ, PKCθ, and receptor for activated C kinase-1) cotranslocate to the uropod. Enhanced intracellular spectrin phosphorylation upon WBH treatment of lymphocytes was also found and could be blocked by the PKC inhibitor bisindolylmaleimide I (GF109203X). These data suggest that the thermal element of fever, as mimicked by these studies, can modulate critical steps in the signal transduction pathways necessary for effective lymphocyte activation and function. Further work is needed to determine the cellular target(s) that transduces the signaling pathway(s) induced by hyperthermia.

Expression of mouse CD43 in the B cell lineage of transgenic mice causes impaired immune responses to T-independent antigens

CD43 (leukosialin), a sialylated glycoprotein expressed on the surface of most hematopoietic cells, has been implicated in cell adhesion and signaling. However, its precise physiological function remains unclear. We used mouse CD43 (mCD43)-immunoglobulin enhancer-transgenic (TG) mice to study the role of mCD43 in vivo. Previous work revealed that mCD43 expression on mature B cells in these mice resulted in immunodeficiency to T-dependent (TD) antigens (Ag), possibly by impairing B-T cell interactions. In the present study we have immunized the TG mice with the T-independent (TI) Ag fluorescein-(Fl) lipopolysaccharide (LPS) (TI type 1 Ag) and Fl-Ficoll (TI type 2 Ag). Surprisingly, the mCD43-Ig enhancer expressing mice were impaired in their ability to mount humoral responses to both Fl-LPS and Fl-Ficoll, and had decreased numbers of cells responding to Ag in vivo. Flow cytometric analysis was performed on peritoneal B-1 cells, a population which often plays a major role in humoral responses to TI Ag such as bacterial Ag. This analysis revealed similar B220, IgM and CD5 expression patterns for the TG and nontransgenic (NTG) B-1 cells. In addition, purified peritoneal B-1 cells from TG and NTG mice were able to respond to LPS. Stimulation of splenic B cells in vitro with Fl-LPS and Fl-Ficoll revealed that, in contrast to NTG B cell responses, TG B cell responses could not be enhanced by co-culture with T cells. However, soluble T cell factor enhancement of the TG B cell responses was normal. These data suggest that the mCD43 expression on B cells may inhibit cell interactions that are important for enhanced TI Ag responses. The anti-adhesive forces of mucins in general may thus be critical in regulating both TD and TI humoral responses.

Disregulated expression of CD43 (leukosialin, sialophorin) in the B cell lineage leads to immunodeficiency

Leukosialin (CD43 or sialophorin) is a cell surface sialoglycoprotein implicated in cell adhesion and proliferation whose tightly regulated expression in B lymphocytes is likely important for their normal development and/or function. To examine the physiologic role of mouse CD43 (mCD43) in vivo, we exploited transgenic (TG) mice whose developmental expression of mCD43 was extended during B cell differentiation so that mCD43 was now expressed on peripheral B cells. Despite having increased B cells, localization of lymphocytes in the TG spleens appeared normal by immunocytochemistry with anti-CD4, anti-CD8, and anti-B220 mAbs. However, the numbers of splenic germinal centers and the resting sera Ig levels were decreased in the TG mice compared with littermate controls. TG mice had decreased humoral responses to the T-dependent Ags keyhole limpet hemocyanin and OVA, as well as reduced Ag-specific B cell numbers. In contrast, in vitro LPS stimulation of purified TG or control B cells resulted in similar proliferation and IgM responses. Thus, the alteration of B cell mCD43 expression that resulted in profound immunodeficiency in vivo was not due to absolute defects in B cell development or Ab production. However, TG B cells had a decreased ability to homotypically aggregate and to present Ag to the T cell hybridoma B3Z. These data suggest that the immunodeficiency seen in vivo is due to the anti-adhesive forces of mCD43 preventing normal T-B cell interaction. This likely reflects a general property of mucins in regulating cell interactions.

Disregulated expression of CD43 (leukosialin, sialophorin) in the B cell lineage leads to immunodeficiency

Leukosialin (CD43 or sialophorin) is a cell surface sialoglycoprotein implicated in cell adhesion and proliferation whose tightly regulated expression in B lymphocytes is likely important for their normal development and/or function. To examine the physiologic role of mouse CD43 (mCD43) in vivo, we exploited transgenic (TG) mice whose developmental expression of mCD43 was extended during B cell differentiation so that mCD43 was now expressed on peripheral B cells. Despite having increased B cells, localization of lymphocytes in the TG spleens appeared normal by immunocytochemistry with anti-CD4, anti-CD8, and anti-B220 mAbs. However, the numbers of splenic germinal centers and the resting sera Ig levels were decreased in the TG mice compared with littermate controls. TG mice had decreased humoral responses to the T-dependent Ags keyhole limpet hemocyanin and OVA, as well as reduced Ag-specific B cell numbers. In contrast, in vitro LPS stimulation of purified TG or control B cells resulted in similar proliferation and IgM responses. Thus, the alteration of B cell mCD43 expression that resulted in profound immunodeficiency in vivo was not due to absolute defects in B cell development or Ab production. However, TG B cells had a decreased ability to homotypically aggregate and to present Ag to the T cell hybridoma B3Z. These data suggest that the immunodeficiency seen in vivo is due to the anti-adhesive forces of mCD43 preventing normal T-B cell interaction. This likely reflects a general property of mucins in regulating cell interactions.